Side protection airbags are used in various modern automobiles. Side protection airbags may be capable of a single and brief deployment which cushions the passenger against a single impact upon the interior of an automobile. Other side protection airbags may be engineered to remain inflated for a relatively longer period of time to protect a passenger against multiple and repetitive impacts within the automobile, as in the case of a vehicle rollover in which the vehicle rolls multiple times following impact.
The manufacture of airbags is labor intensive. Furthermore, the fabric from which airbags are made is costly. It is a goal among airbag designers to minimize wasted fabric which remains following cutting and sewing of an airbag. An airbag design which reduces the number of steps required to assemble or sew a bag, or which reduces waste fabric, or both, is desirable.
Side protection airbags must extend a relatively long distance when deployed along each side window. Many such airbags deploy downward from a storage point located along the upper region of side windows. Typically, such side impact airbags extend from a point near the front windshield to a point near the back windshield of an automobile, along each side. However, there usually is no need for inflatable airbag protection in the area which is directly opposite the seats of the car (i.e. adjacent the door post between front and back doors, for example). It is desirable to make airbags which do not include inflatable portions adjacent the window posts of the automobile.
It is important that airbags, when deployed, exhibit tension along their lower edge. Such tension assists in retaining passengers within the automobile following deployment of the airbag during a crash or rollover event. Furthermore, it is advantageous that front and rear inflatable portions of an airbag be connected near the lower margin of such airbags to provide such tension.
Airbags are cut from relatively long pieces of fabric, sometimes called fabric blanks. The pattern or template employed in such cuttings determines the amount of fabric waste generated during manufacture.
FIG. 1 shows a typical prior art airbag design in which both sides of the inflatable structure are cut as a one-piece unit. The one-piece cutting is folded as shown in FIG. 1A and then sewn to form an inflatable airbag. Relatively large amounts of fabric waste are generated using such a design. FIG. 1B shows one manner in which the airbag configuration of FIG. 1 may be provided in a layout on a fabric blank for cutting.
FIG. 1C shows yet another conventional nesting pattern which results in a fabric usage efficiency of about 75%. By efficiency, it is meant the ratio of the amount of fabric from a fabric blank actually used in the finished airbag product as compared to the total amount of the fabric blank or blanks utilized in the construction of the airbag, in square units. In this particular nesting pattern, both sides (i.e. inboard and outboard) are cut separately as separate fabric pieces. Each side (i.e. inboard and outboard) is cut as one piece, as shown in the FIG. 1C, and may use for example using a material width of fabric blank of about 177.80 centimeters. After cutting, the two pieces may be sewn together to form an inflatable airbag structure.
United States Patent Application Publication US 2002/0167153 A1 to Kippschull (published Nov. 14, 2002; hereafter the “Kippschull publication”) discloses a side curtain airbag having at least two inflation chambers spaced apart from each other. The inflation chambers each have two fabric layers. The region between the two inflation chambers has at most one layer of fabric, in one embodiment. FIG. 1D of the Kippschull specification (which also corresponds to FIG. 1D herein) shows a Kippschull prior art design which uses one piece of fabric positioned between respective inflation chambers. See paragraph 19, Kippschull publication, and FIG. 1D.
In the Kippschull device shown in FIG. 1D, inflation chambers 2,4 are shown. The fabric layer 12 is one piece, or continuous, with only one of the fabric layers of an inflation chamber, not with both chambers. Paragraph 19, line 8, Kippschull publication. The inflation chambers 2 and 4, the cover 8, and the connecting strip 10 also may be manufactured as a separate piece of fabric. Kippschull publication, paragraph 19, line 18.
It is desirable that side protection airbags be economical to manufacture, and yet provide appropriate tension and continuity along their length, thereby providing adequate protection against passenger injury when deployed in an automobile.